1. Field of the Invention
The invention relates to a method for bonding metallic structural elements to form a component, in particular a component for gas turbines. Such components are used for example, as rotor blades or guide vanes and as heat exchanger elements of gas turbines.
2. Description of the Prior Art
In the manufacture of these components, two or more metallic structural elements are preferably permanently bonded together. The bonding of the metallic structural elements was previously carried out by high temperature brazing or by means of diffusion brazing. In high temperature brazing, a nickel or cobalt based braze is used. As is known from W. A. Owczarski in "Process and Metallurgical Factors in Jointing Superalloys and Other High Temperature Materials," Agard LS-91 (1977) 3-1/3-32, diffusion brazing occurs with the formation of a short-term liquid intermediate layer, which latter results from a layer placed in the form of powder or an amorphous foil between the two structural elements to be bonded. A disadvantage of this method is that structural elements with a complex geometrical shape, in particular, cannot be adequately bonded to one another. In addition, pores often appear during high temperature brazing and during diffusion brazing, which pores may be attributed to alterations in density during the solidification process and have an adverse effect on the mechanical properties of the component.
Diffusion welding offers a further possibility of bonding metallic structural elements to form a component. In this case, the two structural elements to be bonded together are welded, under pressure and increased temperatures, by means of pure solid body diffusion. Disadvantages of diffusion welding appear particularly in the bonding of curved surfaces because in this case, very high tolerance requirements are set for the surfaces to be bonded in order to guarantee complete contact. The pressure to be exerted often exceeds 50 MPa and therefore, causes difficulties in the bonding of thin-walled structural elements. In addition, diffusion welding requires a very high temperature so that it demands a very large expenditure of energy.